74 Dart Sport. Hedman Header Hell.

I'll also like to commend the OP for taking on the challenge. Good for you, my young friend! Why that bullshit company purposely MIS spells "Header" is beyond me...
I has a set of the # 78050 headers that were supposed to fit 67-76 318 A body cars. The car was a 73 Dart Sport with a non original 360. Now, despite what some may think, I am no idiot...I have been messing with cars since 1983. I know the tricks to get headers to fit in a Mopar as long as they are built right.
The set I had were crap. The right side collector wanted to share space with the torsion bar. I removed the torsion bar to get them in and a couple of tubes then wanted to hit the STOCK oil pan even though there was still a small gap at the bottom of the head mounting flange...In other words, I'd have to run NO oil pan to get the headers to swing in enough for the flange to sit flat against the head....AND it still interfered with the torsion bar. They were not altered, damaged or dented. They looked fresh from the company. I usually get the right side in first then install the left. This one sucked so bad I just gave up and GAVE them away at a swap meet. The guy was amazed and felt like he really scored.
He did NOT score. He stepped in a soft pile of crap.
I told him they didn't fit but he seemed oblivious, as if I were some idiot and HE knew all the answers.